This invention relates to a fuel vapor recovery system for a motor vehicle, and more particularly to a fuel vapor recovery control valve device in the system.
A fuel vapor recovery system for a motor vehicle as shown in FIG. 1 has been proposed in International Publication PCT/US93/00719. In the system, a fuel vapor recovery valve device, as shown in FIG. 1, is adapted to control the discharge of fuel vapor from a fuel tank 14 having a fuel filler port 12.
More specifically, the device comprises: a housing 16; a first valve assembly 22, which is moved up and down by a diaphragm 42 which divides the space within the housing 16 into an upper chamber 18 and a lower chamber 20; and a second valve assembly (a positive pressure valve) 24 provided in the lower chamber 20. The housing 16 has a vapor recovery port 32 which communicates with a canister 30, a signal port 26 and a first vapor flow-in port 28 on the upper chamber side, and a second vapor flow-in port 34 on the lower chamber side which is controlled (opened and closed) by the second valve assembly 24. The signal port 26 communicates with the fuel filler port 12; the first vapor flow-in port 28 communicates, through a fuel cut-off valve 36, with the fuel tank 14; and the second vapor flow-in port 34 also communicates, through a so-called float valve 38, with the fuel tank 14.
As is apparent from FIG. 1, the first vapor flow-in port 28 is sealingly closed at its lower end. That is, its sealing point corresponds to the central portion of a diaphragm supporting board 40 of relatively large diameter, and thus, the sealing point is far from the operating portion 42a of the diaphragm 42.
Hence, in the case where the diaphragm supporting board 40 is inclined, for instance when the elastic force of a spring 44 applied to the diaphragm supporting board 40 is deflected, it is difficult to absorb the inclination; that is, in this case, it is difficult for the diaphragm 42 to seal closed the first vapor flow-in port 28.
The upper chamber 28 and the lower chamber 20 which are separated in the housing by the diaphragm 42 have no direct communicating path between them. Hence, when vapor flows into the housing from the fuel tank through the fuel cut-off valve 36 and the first vapor flow-in port 28, it may be condensed into liquid. The liquid thus formed may accumulate on the diaphragm with this configuration.